1. Field of the Invention
This invention is directed to methods for preparing lyophilized products suitable for labelling or tagging with a radionuclide, to the radio labelled products themselves and to their use as diagnostic scanning agents. More particularly this invention is directed to lyophilizing a dispersion suitable for radionuclide labelling which contains a protective agent.
2. Description of the Prior Art
Currently there are numerous radiopharmaceutical products useful as diagnostic scanning agents especially, Tc-99m-labelled products. Generally these pharmaceutical products which are usually dispersions of minute particles are radiolabelled shortly before use. Such dispersions must be maintained in a suitable form so they can be labelled and used.
A number of ways are available in the art to keep these dispersions in such a form, namely, freezing or lyophilizing. Of these, lyophilizing is preferred. However, the physical and chemical properties of lyophilized dispersions normally degrade during lyophilization or before radiolabelling which may be 6 to 9 months later. This, of course, is undesirable.
Consequently an improved freeze drying or lyophilization process would be an advancement in the art.